Research Journal of Agriculture and Biological Sciences, 3(5): 498-503, 2007 © 2007, INSInet Publication

Ga3 and Zinc Sprays for Improving Yield and Fruit Quality of Washington Navel Orange Trees Grown under Sandy Soil Conditions 1

Eman, A.A. Abd El-moneim, 2M.M.M. Abd El Migeed and 1Omayma, M.M. Ismail 1

Hort. Crops. Techno. Dept., National Research Centre 2 Pomology Dept, National Research Centre

Abstract: This study was carried out during two successive seasons (2005 and 2006) on ten years old W ashington navel orange trees (Citrus sinensis L. Osbeck) budded on Volkamer lemon (C. volkamerina L.) rootstock, grown in sandy soil in a private orchard at Sadat district, Minufiya G overnorate, Egypt. GA 3 at 10 or 20 ppm was sprayed twice (beginning of April and beginning of June) also,chelated zinc at 0.4% was sprayed three times (mid February, beginning of April and beginning of June). The obtained results revealed that most treatments especially those included zinc sprays improved leaf N, K and Zn contents. However data proved that GA 3 sprays at 20 ppm were more effective than that at 10 ppm in term of fruit set, fruit retention and yield as fruit number or weight (Kg) per tree. Spraying 0.4% chelated zinc alone or with GA 3 especially at 20 ppm significantly increased fruit set, fruit retention, decreased fruit drop and subsequently improved the yield as well as the physical and chemical fruit characteristics. So, spraying 0.4% chelated zinc at mid February followed by spraying 0.4% chelated zinc + 2o ppm GA 3 twice at (beginning of April and beginning of June) seems to be the promising treatment for increasing productivity of low yield W ashington navel orange trees grown under sandy soil condition. Keywords: GA3, Zinc spray, navel orange, leaf mineral content , yield and fruit quality and sandy soil. rates [2 7 ]. Moreover, zinc foliar sprays before anthesis may be beneficial in terms of fruit yield in citrus and grapes Swietlik,[3 3 ]. The positive effects of zinc sprays on nutritional status, fruit set,fruit retention, reducing fruit drop, yield and fruit quality were supported by many investigators, Anora et al., [5 ] on Sweet lime, Shawky et al., [3 1 ] Ismail, [1 4 ], Nahklla,[2 3 ] and Sayed et al., [3 0 ] on oranges. Accordingly, this work was planned as a try to overcome the problem of low yield of W ashington navel orange trees grown under sandy soil conditions through studing the influence of GA 3 and zinc sprays on tree nutritional status, fruit set, fruit drop, fruit retention, yield and fruit quality.

INTRODUCTION In Egypt, citrus is considered the first fruit crop either for local consumption or export demands. Citrus acreage reached 359703 feddans. Oranges represent more than sixty percent of this acreage. W ashington navel, the main orange c.v. occupies about 56% of the total oranges area, most W ashington navel cv. is planted in the old valley while the rest (12%) is found in the newly reclaimed lands [1 9 ] this may be due to inadequate fruit set and sever fruit drop which represent the major causes of navel orange low yield under sandy soil conditions [2 3 ,2 0 ]. The beneficial effects of GA 3 and nutrient elements sprays specially zinc on yield and fruit quality of fruit crops were mentioned by many investigators as Morton,[2 1 ] who found that, GA 3 whether, applied at full bloom or small fruit stage, has significantly increased the number of W ashington navel harvested fruits. Also,the beneficial effects of GA 3 and zinc were suppoted by Agusti et al., [4 ], Abd ElMigeed,[1 ] and Sayed et al.,[3 0 ] on oranges, El-Sese et al., [1 1 ] on mandarin, Mostafa et al., [2 2 ] on pear and ElSharkawy and Mehiesen [1 2 ] on guava. In addition, zinc deficiency is the most common in areas with alkaline soils However, Zn deficiency is corrected by foliar sprays. In this respect, zinc chelate can be applied safely at any time of the growth season at proper

M ATERIALS AND M ETHODS This trial was carried out during two successive seasons (2005 and 2006) on ten years old W ashington navel orange trees (Citrus sinensis L. Osbeck) budded on Volkamer lemon (C. volkamerina L.) rootstock. Trees were planted at 5×5 meters apart on sandy soil under drip irrigation system in a private orchard at Sadat district, Meunofiya Governorate, Egypt. Soil was analyzed by using the methods described by Cottenie et al. [7 ], Table (1). All trees were subjected to the same cultural practices in both studied seasons. Eighteen trees were

Corresponding Author: Eman, A.A. Abd El-moneim, Hort. Crops. Techno. Dept., National Research Center, Egypt. 498

Res. J. Agric. & Biol. Sci., 3(5): 498-503, 2007 selected as uniformed in vigor as possible. The experiment involved six foliage spraying treatments as follows: C C C C C C

Fruit Drop (June Drop): Fruits were counted again on each branch at the end of June and June drop % was determined as follows:

Control (sprayed with water). 10 ppm GA 3 20 ppm GA 3 Zn Zn + 10 ppm GA 3 Zn + 20 ppm GA 3

June drop

No. of retained fruits Fruit retention = ----------------------------------- x100 Total No. Of fruielets In late December, yield per tree was determined as number and weight of fruits (kg)/tree in 2005 and 2006 seasons. For fruit quality a sample of five fruits/tree was randomly taken at harvest to determine fruit weight, fruit diameter, peel thickness, total soluble solids, titratable acidity and ascorbic acid contents using the methods described in [2 ]. The data were subjected to analysis of variance and Duncan's multiple test to differentiate means [9 ].

Leaf M ineral Contents: In late August of each season, forty leaves of 5-7 months old from tagged non-fruiting and non-flushing terminals of spring growth cycle were collected [1 6 ].Leaf samples were washed with tap water, then with distilled water and dried at 70 ºC until constant weight, finally, ground and digested using the method of Piper[2 6 ]. The digested solution was used for the determination of each of N using micro kjeldahel menthod outlined by Jackson [1 5 ]. Phosphorus by using the method of W alanabe and Olsen [3 5 ]. K and Zn, by using Atomic Absorption Spectrophotometer "Perkin Elmer 1100 B" after [6 ]. The above mentioned nutrients were calculated as percentage on dry weight basis except Zn was calculated as ppm on dry weight basis

RESULTS AND DISCUSSIONS Leaf M ineral Content: Results in Table (2) showed that GA 3 and zinc sprays alone or in combinations increased N content in the leaves compared with the control. However, this effect was more pronounced in the second season. Highest leaf N content was obtained from trees sprayed with 20 ppm GA 3 + 0.4 % chelated zinc (T 6 ). The lowest N content in the leaves in both seasons was obtained from the control. Regarding P content in the leaves, results revealed that GA 3 and/or zinc sprays slightly increased its values than those of the control. However, no significant differences in P leaf content among treatments were developed in both seasons. Potassium content in the leaves was increased by treatments included zinc sprays compared with the control. However GA 3 sprays only at the high concentration (20 ppm) slightly and insignificantly increased K content in the leaves than the control. Results in Table (2) indicated that spraying zinc alone or with G A 3 significantly increased Zn content in the leaves compared with the control or GA 3 sprays alone. However, GA 3 and/or zinc raised Zn content in the leaves from the low to the optimum range (25-100 ppm) Jones and Embleton [1 7 ]. From the above results, it obvious that spraying GA 3 specially at

Number of Flowers: The number of flowers at full bloom was counted for each labeled branch. Fruit Set: The numbers of fruit set two weeks after full bloom were counted and fruit set % was estimated according to the following equation

=

x100

Fruit Retention: The number of fruits retained till harvest time on the same branch was counted and fruit retention estimated.

W here GA 3 = gibberellic acid (berelex), Zn = 0.4 % chelated zinc (12 % Zn). A complete randomized block design was arranged where each treatment was replicated three times on one – tree / plots. GA 3 at 10 or 20 ppm was sprayed twice (at beginning of April and beginning of June). Zinc was sprayed three times (on mid February, beginning of April and beginning of June) in 2005 and 2006 seasons. All trees received the spraying solution (about ten liters/ tree) till run off. Misrol liquid soap (1ml/l) was used as a wetting agent. Eight shoots of about 2.5 cm diameter at the same height around each tree were chosen, two of them toward each direction were labeled during the current spring growth cycle to carry out the following measurements:

fruit set

=

Total No. Of fruitlets No. of fruits in late June ---------------------------------Total No. Of fruitlets

Total No. of fruitlets ----------------------------------- x100 Total No. Of flowers

499

Res. J. Agric. & Biol. Sci., 3(5): 498-503, 2007 Table 1: Physical and chem ical soil analysis a- M echanical analysis: Sand,% Silt,% Clay,% 90 5 5 b- Chem ical analysis: Soluble cations,m eq/1 ------------------------------------------------------pH(1:2.5) EC{1:1}dsm -1 CaCo 3 % N ppm K Na Ca Mg 8.2 1.5 5.5 trace 0.57 9.18 2.65 2.4

Texture Sandy Soluble anions, m eq/1 ------------------------------------------------------Cl So 4 HCO 3 m g/l CO 3 5.3 5.65 3.85 ----

Table 2: Effect of GA 3 and/or zinc sprays on N , P, K and Zn contents of W ashington navel orange leaves in 2005 and 2006 seasons. N o. N % P % K % Zn ppm ---------------------------------------------------------------------------------------------------------Treatm ents 2005 2006 2005 2006 2005 2006 2005 2006 1- Control 2.15 2.10 b 0.12 0.14 1.2 1.17 b 19 b 23 c ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------2- 10 ppm GA3 2.19 2.27 a 0.16 0.15 1.19 1.09 b 18 b 25 c ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3- 20 ppm GA3 2.25 2.32 a 0.16 0.16 1.26 1.20 b 19 b 25 c ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4- Zn 2.23 2.30 a 0.14 0.15 1.2 1.35 a 37 a 46 b ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5- Zn + 10 ppm GA3 2.3 2.31 a 0.15 0.16 1.33 1.42 a 48 a 57 a ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------6- Zn + 20 ppm GA3 2.32 2.39 a 0.14 0.16 1.2 1.35 a 37 a 41 b ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Significance at 5% level NS S NS NS NS S S S M eans having the sam e letters within a colum n are not significantly different at 5% level.S: significantN S: not significant

present results were supported by El Sese [1 1 ], on Balady mandarin and El–Sharkawy and Mehaisen [1 2 ], on guava trees. Similarly, the obtained results are in agreement with Nakhlla [2 3 ] on Navel orange, who found that chelated Zn sprays at 0.4% significantly increased fruit set percentage.

the high concentration in combination with zinc had improved the nutritional status of W ashington navel orange trees in term of N, K and Zn contents in the leaves. Such results were supported by Nijjar [2 4 ] who mentioned that GA 3 seems to be compatible with micronutrients sprays. The obtained results are in line with the findings of Samra [2 9 ] who found that spaying Balady mandarin with zinc increased N content in the leaves. Similarly, the present results are in agreement with those reported by Dawood et al, [8 ] who found that GA 3 sprays enhanced leaf N content in Balady mandarin. Also, these findings are in accordance with those mentioned by Sayed et al, [3 0 ] who noticed that foliar application of GA 3 and zinc having a positive effect on leaf mineral content in Valencia orange trees.

Fruit Drop: Results in Table (3) indicated that GA 3 and or zinc sprays markedly decreased fruit drop. Generally, fruit drop was higher in the first season than in the second one. However, a particular trend noticed in this concern, that GA 3 sprays decreased fruit drop compared to the control, this effect was more cleared in the 2005 season. Similarly, zinc sprays decreased fruit drop than that of the control or those sprayed with GA 3 alone. The lowest fruit drop obtained from trees sprayed with zinc + GA 3 at 10 ppm. The present results are in agreement with the findings obtained by Agusti[3 ] who concluded that the reduction in fruit drop as a response of GA 3 treatments might be due to an increase in initial growth of ovaries and reduce magnitude the peak of abscission. Moreover, the reduction in fruit drop obtained due to zinc sprays could be attributed to its effect on enhancing formation and translocation of carbohydrates and carbohydrate enzymes [3 6 ].

Fruit Set: Data as shown in Table (3) cleared that GA 3 at 20 ppm and/or zinc sprays significantly increased fruit set in both seasons compared with the control or GA 3 at 10 ppm treatments. Highest fruit set was obtained from the trees received GA 3 with zinc sprays, while the lowest fruit set was obtained from the control.The obtained results proved that spraying GA 3 at 20ppm as well as chelated Zn at 0.4 % has a positive effect on increasing fruit set. In this respect, many investigators noticed that exogenous application of gibberellins was effective in increasing fruit set of Clementine mandarin [3 2 ] . The obtained results are in harmony with the findings obtained by Agusti et al.,[4 ] who proved that GA 3 sprays at petal fall enhanced fruit set of Sweet orange tree. Also, the

Fruit Retention: As shown in Table (3) results indicate that GA 3 and/or zinc sprays significantly increased fruit retention over the control. Spraying 0.4% chelated zinc+20 ppm GA 3 recorded high

500

Res. J. Agric. & Biol. Sci., 3(5): 498-503, 2007 Table 3: Effect of GA 3 and/or zinc sprays on fruit set, fruit drop, fruit retention and yield of W ashington navel orange trees in 2005 and 2006 seasons. N o. N o. of fruit/ tree Fruit set % Fruit drop % Fruit retention % Y ield (kg) / tree --------------------------------------------------------------------------------------------------------------------------------------Treatm ents 2005 2006 2005 2006 2005 2006 2005 2006 2005 2006 1- Control 125b 127c 20.4c 27.9b 80.7a 73.9a 34.7c 36.2c 34.7c 36.2c ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------2- 10 ppm GA3 151b 169b 22.7c 28.5b 77.2a 69.8b 42.9bc 50.5ab 42.9bc 50.5ab ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3- 20 ppm GA3 179a 185b 28.0b 34.5a 77.5a 69.6b 53.1ab 52.9ab 53.1ab 52.9ab ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4- Zn 190a 202ab 33.7a 35.6a 66.3b 54.7c 52.3ab 60.7ab 52.3ab 60.7ab ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5- Zn+ 10 ppm GA3 198a 228a 35.4a 38.3a 52.8c 51.7c 57.2a 61.9ab 57.2a 61.9ab ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------6- Zn+ 20 ppm GA3 206a 228a 36.1a 37.5a 53.1c 53.0c 62.1a 68.3a 62.1a 68.3a ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Significance at 5 % level S S S S S S S S S S M eans having the sam e letters within a colum n are not significantly different at 5% level.S: significant Table 4: Effect of GA 3 and/or zinc sprays on som e physical and chem ical fruit characteristics of W ashington navel orange trees in 2005 and 2006 seasons Fruit weight Fruit diam eter Peel thickness Acidity T.S.S Ascorbic acid N o. (gm ) (cm ) (cm ) (% ) % (m g/100 m l juice) -----------------------------------------------------------------------------------------------------------------------------------------Treatm ents 2005 2006 2005 2006 2005 2006 2005 2006 2005 2006 2005 2006 1- Control 273c 277 6.43b 6.90c 0.42b 0.40b 0.81 0.80b 9.8c 10.0b 42 41d ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------2- 10 ppm GA3 298ab 285 7.13ab 7.33b 0.45b 0.48ab 0.85 0.82ab 10.2bc 10.4b 43 42cd ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------3- 20 ppm GA3 285bc 296 7.00ab 7.50ab 0.48b 0.55ab 0.84 0.83ab 10.5abc 10.6b 43 43cd ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------4- Zn 304ab 286 7.53a 7.63ab 0.57a 0.59ab 0.84 0.79b 11.5a 11.6a 49 47bc ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------5- Zn+ 10 ppm GA3 311a 284 7.73a 7.75a 0.60a 0.58ab 0.85 0.83ab 11.3a 12.0a 50 50a ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------6- Zn+ 20 ppm GA3 314a 302 8.0a 7.80a 0.61a 0.60a 0.86 0.87a 11.5a 11.6a 50 53a ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Significance S NS S S S S NS S S S NS S at 5 % level M eans having the sam e letters within a colum n are not significantly different at 5% level.S: significantN S: not significant

fruit retention values in both seasons. In this respect, Nijjar[2 4 ], mentioned that zinc is required for preventing the abscission layer formation and consequently, the reduction in pre-harvest dropping. The obtained results are in line with those found by Anora et al., [5 ] who mentioned that double zinc sprays at 0.5 % increased final fruit retention of Sweet lime. Similar results were obtained by Gregoriu et al.,[1 3 ] who found that GA 3 has a preventive effect on June and pre-harvest drop in oranges.

The obtained results of GA 3 sprays are in line with those reported by El-Sese [1 1 ] who found that Balady mandarin trees sprayed at full bloom with GA 3 resulted in increased yield as number or weight (Kg) of fruits/ tree. The obtained results also supported by Agusti et al.,[4 ] ) on Sweet orange, Mostafa et al., [2 2 ] on pear, Abd El-Migeed [1 ] on W ashington navel and ElSharkawy and Mehaisen [1 2 ] on guava. Increasing yield due to GA 3 or zinc sprays may be attributed to their effects on increasing levels of IAA more than increasing fruit set[3 4 ], Nakhlla [2 3 ] and Raphael et al., [2 8 ]. Simillarly the present results were supported by the findings obtained by Shawky et al., [3 1 ] Ismail [1 4 ] who found that foliar application of zinc increased yield of Navel and Valencia oranges. Also, Swietlik [3 3 ] concluded that zinc foliar sprays applied before anthesis may be most beneficial in terms of fruit yield in citrus and grapes. It could be concluded that the enhancement previously mentioned in yield may be attributed to the improvement in the nutritional status specially zinc.

Yield: Yield as number or weight (Kg) of fruits per tree as shown in Table (3) increased by most tested treatments in 2005 and 2006 seasons than the control. In this respect, a particular trend was noticed that GA 3 sprays at the high concentration (20 ppm) was more effective in improving yield than spraying GA 3 at 10 ppm. Moreover, spraying zinc alone or in combination with GA 3 at any concentration significantly increased yield in the two seasons comparing with the control. Highest yield obtained from trees sprayed with 20 ppm GA 3 + 0.4 % chelated zinc. 501

Res. J. Agric. & Biol. Sci., 3(5): 498-503, 2007 Fruit Quality: Data in Table (4) show the effect of GA 3 and/or zinc sprays on some physical and chemical fruit properties of Washington navel orange trees in 2005 and 2006 seasons.

the same trend obtained by different treatments on juice acidity. However, treatments included zinc significantly increased V.C in fruit juice than the control. High V.C obtained by spraying zinc and GA 3 sprays. This means that the presence of GA 3 irrespective to its concentration with zinc sprays has a positive effect on vitamin C in fruit juice. This effect obviously noticed in 2006 season. The present results are in line with the findings obtained by El-Menshawi et al., [1 0 ] who concluded that zinc sprays increased fruit weight, peel thickness, TSS and V.C in Balady mandarin trees. Similarly, Nakhlla [2 3 ] on Navel orange reported that Zn sprays increased TSS and V.C contents of the fruits. It could be noticed from the present study that GA 3 is not only compatible with nutrient elements i.e. zinc on nutritional status, Najjar [2 4 ], but proved that GA 3 is also compatible with zinc in terms of yield as well as fruit quality. From the above mentioned results, it could be concluded that spraying 0.4% chelated zinc at mid February followed by spraying 0.4% chelated zinc + 2o ppm GA 3 twice at (beginning of April and beginning of June) seems to be the promising treatment not only to overcome the low yield problem of W ashington navel orange trees grown under sandy soil condition but also for improving fruit quality.

Physical Properties: Fruit weight (gm). As shown in Table (4),fruit weight improved by all treatments comparing with the control. However, this effect was more noticed in the first season. Highest fruit weight was obtained from trees sprayed with0.4% chelated Zn + 20 ppm GA 3 while, fruits taken from the control trees recorded the lowest fruit weight values in both seasons. Peel thickness (cm) slightly and insignificantly increased by GA 3 sprays. However, spraying zinc alone or with GA 3 at 20 ppm significantly increased peel thickness compared with the control that gave the lowest peel thickness values in the two seasons. Fruit diameter (cm).Table (4) showed that fruit diameter improved by most tested treatments. Spraying zinc alone or with GA 3 at any concentration markedly increased fruit diameter comparing with the control. From the above results it seems that physical fruit properties in terms of fruit weight, peel thickness and fruit diameter was improved by most treatments specially those included zinc sprays. The role of GA 3 in improving fruit quality namely, fruit weight, peel thickness and fruit diameter may explained due to its role in increasing cell elongation, Pharis and King [2 5 ]. However, the present results supported by the findings obtained by Sayed et al.,[3 0 ] who found that fruit weight, peel thickness and fruit diameter of Valencia orange were increased due to GA 3 sprays. The improvement occurred in fruit quality due to supplying trees with zinc could be attributed to its effects on enhancing formation and translocation of carbohydrates and carbohydrate enzymes [3 6 ].

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Chemical Properties: Total soluble solids (TSS). Results in Table (4) showed that GA 3 sprays slightly increased TSS compared to the control in both seasons. However, spraying zinc alone or with GA 3 significantly increased TSS than the control. This means that the significant increase in TSS was mainly due zinc not to GA 3 . Acidity. Data in Table (4) cleared that juice acidity was significantly affected in the second season. Spraying zinc +20 ppm GA 3 significantly increased juice acidity compared with the control or with those sprayed with zinc alone. This means that the presence of GA 3 at the high concentration (20 ppm) with zinc sprays tended to increase juice acidity. This may be due to the effect of GA 3 on delaying maturity. Ju et al.,[1 8 ]. Ascorbic acid (V.C). Data in Table (4) indicated that (V.C) content in fruit juice, followed in general,

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